A process of manufacturing a semiconductor device in which a stacking structure of an integrated circuit is formed on the surface of a target substrate such as a semiconductor wafer (hereinafter, referred to as a wafer) includes a process of processing the wafer surface by using a liquid to remove minute dusts or a native oxide layer on the wafer surface with a cleaning liquid such as a chemical liquid.
For example, a single type spin cleaning apparatus that performs wafer cleaning rotates the wafer while supplying an alkaline or acid chemical liquid onto the surface of the wafer by using a nozzle to remove dusts or a native oxide on the wafer surface. In this case, after remaining chemical liquids are removed from the wafer surface by rinse cleaning using deionized water, the wafer surface is dried by a spin drying where the remaining liquids are brushed away while rotating the wafer.
However, with the high integration of the semiconductor device, a problem such as so-called a pattern collapse has grown seriously during the processing of removing the liquids. The pattern collapse is a phenomenon in which the balance of a surface tension horizontally pulling a convex portion is lost, and as a result, the convex portion falls down toward the side where more liquids remain at the time of drying the remaining liquids on the wafer surface, as the remaining liquids at, for example, the left and right sides of the convex portion of concave and convex portions forming a pattern are unevenly dried.
As a technique of removing the remaining liquids on the wafer surface while preventing the pattern collapse from occurring, a drying method using a fluid in a supercritical state or subcritical state (hereinafter, collectively referred to as a high-pressure fluid) has been known. The viscosity of the high-pressure fluid is lower than a liquid while the ability to dissolve thereof is higher than the liquid. Further, there is no interface between the high-pressure fluid and a liquid or a gas that is in equilibrium state with the high-pressure fluid. Therefore, the liquid attached to the wafer is substituted with the high-pressure fluid, and thereafter, when the high-pressure fluid is changed to a gaseous state, the liquid can be dried without being influenced by the surface tension.
Herein, in Japanese Patent Application Laid-Open No. 2008-72118 (see, for example, paragraphs [0025] to [0029], paragraphs [0038] and [0039], and FIG. 1), disclosed is a technology in which a substrate cleaned in a cleaning unit is carried to a dry processing chamber, and thereafter, the pressure in the dry processing chamber is raised, in advance, to be equal to or higher than threshold pressure of a dry processing fluid (in the present exemplary embodiment, carbon dioxide), and thereafter, a supercritical-state dried fluid is supplied to the dry processing chamber to dry the substrate. In the technology, the dried fluid which is subjected to the completion of the processing is discharged from the dry processing chamber and the inside of the dry processing chamber is depressurized to atmospheric pressure, such that the dry processing is terminated.